diff options
Diffstat (limited to 'src/random.cpp')
| -rw-r--r-- | src/random.cpp | 203 |
1 files changed, 168 insertions, 35 deletions
diff --git a/src/random.cpp b/src/random.cpp index 6634019be..3b9df3eda 100644 --- a/src/random.cpp +++ b/src/random.cpp @@ -16,11 +16,26 @@ #include <stdlib.h> #include <limits> +#include <chrono> +#include <thread> #ifndef WIN32 #include <sys/time.h> #endif +#ifdef HAVE_SYS_GETRANDOM +#include <sys/syscall.h> +#include <linux/random.h> +#endif +#ifdef HAVE_GETENTROPY +#include <unistd.h> +#endif +#ifdef HAVE_SYSCTL_ARND +#include <sys/sysctl.h> +#endif + +#include <mutex> + #include <openssl/err.h> #include <openssl/rand.h> @@ -32,15 +47,22 @@ static void RandFailure() static inline int64_t GetPerformanceCounter() { - int64_t nCounter = 0; -#ifdef WIN32 - QueryPerformanceCounter((LARGE_INTEGER*)&nCounter); + // Read the hardware time stamp counter when available. + // See https://en.wikipedia.org/wiki/Time_Stamp_Counter for more information. +#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64)) + return __rdtsc(); +#elif !defined(_MSC_VER) && defined(__i386__) + uint64_t r = 0; + __asm__ volatile ("rdtsc" : "=A"(r)); // Constrain the r variable to the eax:edx pair. + return r; +#elif !defined(_MSC_VER) && (defined(__x86_64__) || defined(__amd64__)) + uint64_t r1 = 0, r2 = 0; + __asm__ volatile ("rdtsc" : "=a"(r1), "=d"(r2)); // Constrain r1 to rax and r2 to rdx. + return (r2 << 32) | r1; #else - timeval t; - gettimeofday(&t, NULL); - nCounter = (int64_t)(t.tv_sec * 1000000 + t.tv_usec); + // Fall back to using C++11 clock (usually microsecond or nanosecond precision) + return std::chrono::high_resolution_clock::now().time_since_epoch().count(); #endif - return nCounter; } void RandAddSeed() @@ -80,7 +102,7 @@ static void RandAddSeedPerfmon() if (ret == ERROR_SUCCESS) { RAND_add(vData.data(), nSize, nSize / 100.0); memory_cleanse(vData.data(), nSize); - LogPrint("rand", "%s: %lu bytes\n", __func__, nSize); + LogPrint(BCLog::RAND, "%s: %lu bytes\n", __func__, nSize); } else { static bool warned = false; // Warn only once if (!warned) { @@ -91,34 +113,86 @@ static void RandAddSeedPerfmon() #endif } +#ifndef WIN32 +/** Fallback: get 32 bytes of system entropy from /dev/urandom. The most + * compatible way to get cryptographic randomness on UNIX-ish platforms. + */ +void GetDevURandom(unsigned char *ent32) +{ + int f = open("/dev/urandom", O_RDONLY); + if (f == -1) { + RandFailure(); + } + int have = 0; + do { + ssize_t n = read(f, ent32 + have, NUM_OS_RANDOM_BYTES - have); + if (n <= 0 || n + have > NUM_OS_RANDOM_BYTES) { + RandFailure(); + } + have += n; + } while (have < NUM_OS_RANDOM_BYTES); + close(f); +} +#endif + /** Get 32 bytes of system entropy. */ -static void GetOSRand(unsigned char *ent32) +void GetOSRand(unsigned char *ent32) { -#ifdef WIN32 +#if defined(WIN32) HCRYPTPROV hProvider; int ret = CryptAcquireContextW(&hProvider, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT); if (!ret) { RandFailure(); } - ret = CryptGenRandom(hProvider, 32, ent32); + ret = CryptGenRandom(hProvider, NUM_OS_RANDOM_BYTES, ent32); if (!ret) { RandFailure(); } CryptReleaseContext(hProvider, 0); -#else - int f = open("/dev/urandom", O_RDONLY); - if (f == -1) { +#elif defined(HAVE_SYS_GETRANDOM) + /* Linux. From the getrandom(2) man page: + * "If the urandom source has been initialized, reads of up to 256 bytes + * will always return as many bytes as requested and will not be + * interrupted by signals." + */ + int rv = syscall(SYS_getrandom, ent32, NUM_OS_RANDOM_BYTES, 0); + if (rv != NUM_OS_RANDOM_BYTES) { + if (rv < 0 && errno == ENOSYS) { + /* Fallback for kernel <3.17: the return value will be -1 and errno + * ENOSYS if the syscall is not available, in that case fall back + * to /dev/urandom. + */ + GetDevURandom(ent32); + } else { + RandFailure(); + } + } +#elif defined(HAVE_GETENTROPY) + /* On OpenBSD this can return up to 256 bytes of entropy, will return an + * error if more are requested. + * The call cannot return less than the requested number of bytes. + */ + if (getentropy(ent32, NUM_OS_RANDOM_BYTES) != 0) { RandFailure(); } +#elif defined(HAVE_SYSCTL_ARND) + /* FreeBSD and similar. It is possible for the call to return less + * bytes than requested, so need to read in a loop. + */ + static const int name[2] = {CTL_KERN, KERN_ARND}; int have = 0; do { - ssize_t n = read(f, ent32 + have, 32 - have); - if (n <= 0 || n + have > 32) { + size_t len = NUM_OS_RANDOM_BYTES - have; + if (sysctl(name, ARRAYLEN(name), ent32 + have, &len, NULL, 0) != 0) { RandFailure(); } - have += n; - } while (have < 32); - close(f); + have += len; + } while (have < NUM_OS_RANDOM_BYTES); +#else + /* Fall back to /dev/urandom if there is no specific method implemented to + * get system entropy for this OS. + */ + GetDevURandom(ent32); #endif } @@ -129,6 +203,10 @@ void GetRandBytes(unsigned char* buf, int num) } } +static std::mutex cs_rng_state; +static unsigned char rng_state[32] = {0}; +static uint64_t rng_counter = 0; + void GetStrongRandBytes(unsigned char* out, int num) { assert(num <= 32); @@ -144,8 +222,17 @@ void GetStrongRandBytes(unsigned char* out, int num) GetOSRand(buf); hasher.Write(buf, 32); + // Combine with and update state + { + std::unique_lock<std::mutex> lock(cs_rng_state); + hasher.Write(rng_state, sizeof(rng_state)); + hasher.Write((const unsigned char*)&rng_counter, sizeof(rng_counter)); + ++rng_counter; + hasher.Finalize(buf); + memcpy(rng_state, buf + 32, 32); + } + // Produce output - hasher.Finalize(buf); memcpy(out, buf, num); memory_cleanse(buf, 64); } @@ -177,21 +264,67 @@ uint256 GetRandHash() return hash; } -FastRandomContext::FastRandomContext(bool fDeterministic) +void FastRandomContext::RandomSeed() { - // The seed values have some unlikely fixed points which we avoid. - if (fDeterministic) { - Rz = Rw = 11; - } else { - uint32_t tmp; - do { - GetRandBytes((unsigned char*)&tmp, 4); - } while (tmp == 0 || tmp == 0x9068ffffU); - Rz = tmp; - do { - GetRandBytes((unsigned char*)&tmp, 4); - } while (tmp == 0 || tmp == 0x464fffffU); - Rw = tmp; - } + uint256 seed = GetRandHash(); + rng.SetKey(seed.begin(), 32); + requires_seed = false; +} + +FastRandomContext::FastRandomContext(const uint256& seed) : requires_seed(false), bytebuf_size(0), bitbuf_size(0) +{ + rng.SetKey(seed.begin(), 32); } +bool Random_SanityCheck() +{ + uint64_t start = GetPerformanceCounter(); + + /* This does not measure the quality of randomness, but it does test that + * OSRandom() overwrites all 32 bytes of the output given a maximum + * number of tries. + */ + static const ssize_t MAX_TRIES = 1024; + uint8_t data[NUM_OS_RANDOM_BYTES]; + bool overwritten[NUM_OS_RANDOM_BYTES] = {}; /* Tracks which bytes have been overwritten at least once */ + int num_overwritten; + int tries = 0; + /* Loop until all bytes have been overwritten at least once, or max number tries reached */ + do { + memset(data, 0, NUM_OS_RANDOM_BYTES); + GetOSRand(data); + for (int x=0; x < NUM_OS_RANDOM_BYTES; ++x) { + overwritten[x] |= (data[x] != 0); + } + + num_overwritten = 0; + for (int x=0; x < NUM_OS_RANDOM_BYTES; ++x) { + if (overwritten[x]) { + num_overwritten += 1; + } + } + + tries += 1; + } while (num_overwritten < NUM_OS_RANDOM_BYTES && tries < MAX_TRIES); + if (num_overwritten != NUM_OS_RANDOM_BYTES) return false; /* If this failed, bailed out after too many tries */ + + // Check that GetPerformanceCounter increases at least during a GetOSRand() call + 1ms sleep. + std::this_thread::sleep_for(std::chrono::milliseconds(1)); + uint64_t stop = GetPerformanceCounter(); + if (stop == start) return false; + + // We called GetPerformanceCounter. Use it as entropy. + RAND_add((const unsigned char*)&start, sizeof(start), 1); + RAND_add((const unsigned char*)&stop, sizeof(stop), 1); + + return true; +} + +FastRandomContext::FastRandomContext(bool fDeterministic) : requires_seed(!fDeterministic), bytebuf_size(0), bitbuf_size(0) +{ + if (!fDeterministic) { + return; + } + uint256 seed; + rng.SetKey(seed.begin(), 32); +} |